[PATCH 4/6] mmc: host: sdhci-esdhc-imx.c: correct the auto-tuning setting for sdio device

Tue Aug 17 01:00:56 PDT 2021

On Tue, 17 Aug 2021 at 08:57, Bough Chen <haibo.chen at nxp.com> wrote:
>
> > -----Original Message-----
> > From: Ulf Hansson [mailto:ulf.hansson at linaro.org]
> > Sent: 2021年8月16日 21:53
> > To: Bough Chen <haibo.chen at nxp.com>
> > Cc: Adrian Hunter <adrian.hunter at intel.com>; Shawn Guo
> > <shawnguo at kernel.org>; Rob Herring <robh+dt at kernel.org>; Sascha Hauer
> > <s.hauer at pengutronix.de>; Sascha Hauer <kernel at pengutronix.de>; Fabio
> > Estevam <festevam at gmail.com>; linux-mmc <linux-mmc at vger.kernel.org>;
> > dl-linux-imx <linux-imx at nxp.com>; DTML <devicetree at vger.kernel.org>; Linux
> > ARM <linux-arm-kernel at lists.infradead.org>
> > Subject: Re: [PATCH 4/6] mmc: host: sdhci-esdhc-imx.c: correct the auto-tuning
> > setting for sdio device
> >
> > On Mon, 16 Aug 2021 at 15:00, <haibo.chen at nxp.com> wrote:
> > >
> > > From: Haibo Chen <haibo.chen at nxp.com>
> > >
> > > USDHC contain auto tuning circuit, this circuit will work
> > > automatically after the tuning procedurae, it can increase/decrease
> > > the delay cell according to the outside environment change (like
> > temperature).
> > >
> > > Unfortunately, this auto tuning circuit can not handle the async sdio
> > > device interrupt correctly. When sdio device use 4 data line, async
> > > sdio interrupt will use DAT[1], if we enable auto tuning circuit check
> > > 4 data lines, include the DAT[1], this circuit will detect this
> > > interrupt, take this as a data on DAT[1], and adjust the delay cell wrongly.
> > >
> > > This is the hardware design limitation, to avoid this, when sdio
> > > device enable async interrupt, auto tuning circuit only check DAT[0] and CMD
> > lines.
> >
> > SDIO irqs are being enabled/disabled dynamically in runtime by the mmc core
> > via the host ops ->enable_sdio_irq().
> >
> > Rather than forcing the autotuning circuit to stay unused statically, perhaps an
> > option would be to disable it when the SDIO irqs becomes enabled? Or maybe
> > that becomes too complicated?
>
> For interrupt in 4-bit mode, there is a definition of interrupt period, only in this period can the interrupt be
> detect and recognize. The interrupt period can exist during data transfer.
>
> So to fix this issue, one method is to disable auto tuning circuit. Another is my current method, just detect CMD
> and DAT0, but at least auto tuning still can work (this method need board design keep align all data lines).

To allow DAT1 being used for SDIO irqs (async or not), the irqs needs
to be enabled internally in the SDIO card first. This is done by
writing to the CCCR register, which happens in sdio_claim_irq(). At
this point in sdio_claim_irq() the core also invokes the
->enable_sdio_irq() host ops, to allow the host to prepare itself to
accept SDIO irqs.

It sounds to me that you should be able to use the ->enable_sdio_irq
ops, as a way of understanding that the auto-tuning feature also needs
to be turned off, because it's not compatible with SDIO irqs.

Kind regards
Uffe

>
>
> Best Regards
> Haibo chen
>
> >
> > >
> > > Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
> > > ---
> > >  drivers/mmc/host/sdhci-esdhc-imx.c | 18 ++++++++++++++++++
> > >  1 file changed, 18 insertions(+)
> > >
> > > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> > > b/drivers/mmc/host/sdhci-esdhc-imx.c
> > > index f18d169bc8ff..ab84c29777e5 100644
> > > --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> > > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> > > @@ -226,6 +226,7 @@ struct esdhc_platform_data {
> > >         unsigned int tuning_step;       /* The delay cell steps in tuning
> > procedure */
> > >         unsigned int tuning_start_tap;  /* The start delay cell point in
> > tuning procedure */
> > >         unsigned int strobe_dll_delay_target;   /* The delay cell for
> > strobe pad (read clock) */
> > > +       bool sdio_async_interrupt_enabled;      /* sdio device enable
> > the async interrupt */
> > >  };
> > >
> > >  struct esdhc_soc_data {
> > > @@ -416,6 +417,8 @@ static inline void
> > > esdhc_wait_for_card_clock_gate_off(struct sdhci_host *host)
> > >  /* Enable the auto tuning circuit to check the CMD line and BUS line
> > > */  static inline void usdhc_auto_tuning_mode_sel(struct sdhci_host
> > > *host)  {
> > > +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > > +       struct pltfm_imx_data *imx_data =
> > > + sdhci_pltfm_priv(pltfm_host);
> > >         u32 buswidth, auto_tune_buswidth;
> > >
> > >         buswidth = USDHC_GET_BUSWIDTH(readl(host->ioaddr +
> > > SDHCI_HOST_CONTROL)); @@ -432,6 +435,18 @@ static inline void
> > usdhc_auto_tuning_mode_sel(struct sdhci_host *host)
> > >                 break;
> > >         }
> > >
> > > +       /*
> > > +        * If sdio device use async interrupt, it will use DAT[1] to signal
> > > +        * the device's interrupt asynchronous when use 4 data lines.
> > > +        * Then hardware auto tuning circuit MUST NOT check the DAT[1]
> > line,
> > > +        * otherwise auto tuning will be impacted by this async interrupt,
> > > +        * and change the delay cell incorrectly, which then cause
> > data/cmd
> > > +        * errors.
> > > +        * This is the hardware auto tuning circuit limitation.
> > > +        */
> > > +       if (imx_data->boarddata.sdio_async_interrupt_enabled)
> > > +               auto_tune_buswidth =
> > > + ESDHC_VEND_SPEC2_AUTO_TUNE_1BIT_EN;
> > > +
> > >         esdhc_clrset_le(host,
> > ESDHC_VEND_SPEC2_AUTO_TUNE_MODE_MASK,
> > >                         auto_tune_buswidth |
> > ESDHC_VEND_SPEC2_AUTO_TUNE_CMD_EN,
> > >                         ESDHC_VEND_SPEC2); @@ -1531,6 +1546,9
> > @@
> > > sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
> > >         if (of_property_read_u32(np, "fsl,delay-line",
> > &boarddata->delay_line))
> > >                 boarddata->delay_line = 0;
> > >
> > > +       if (of_property_read_bool(np,
> > > + "fsl,sdio-async-interrupt-enabled"))
> >
> > As stated on the DT patch, I think you can use the "cap-sdio-irq" instead.
> >
> > > +               boarddata->sdio_async_interrupt_enabled = true;
> > > +
> > >         mmc_of_parse_voltage(host->mmc, &host->ocr_mask);
> > >
> > >         if (esdhc_is_usdhc(imx_data) && !IS_ERR(imx_data->pinctrl)) {
> > > --
> > > 2.17.1
> > >
> >
> > Kind regards
> > Uffe